The present application incorporates the provisional U.S. application 61/346,923 filed May 21, 2010 by reference.
The present invention relates to a process for preparing 2-(2-tert-butylaminoethoxy)ethanol (tert-butylaminodiglycol, TBADG) by reacting diethylene glycol (DG) with tert-butylamine (TBA) in the presence of hydrogen and of a copper catalyst.
One use of the process product is that in gas scrubbing, for example, for the selective separation of acidic gases, for example H2S from gas streams which comprise mixtures of one or more acidic gases and CO2.
EP 137 478 A2 (BASF AG) relates to a process for preparing N-methylpiperidine or N-methylmorpholine by catalytically aminating pentanediols or diethylene glycol with methylamine in the gas phase over a copper catalyst which has been obtained by heat treatment of a basic copper- and aluminum-comprising carbonate.
EP 235 651A1 (BASF AG) teaches a process for preparing N-methylpiperazine from diethanolamine and methylamine over metallic catalysts. The reaction is performed in the liquid phase (trickle mode) (page 3 last paragraph). According to the example, a Cu/Al2O3 catalyst is used.
EP 816 350 A1 (BASF AG) describes processes for preparing N-methylpiperidine and N-methylmorpholine by reacting primary amine with a diol over a copper catalyst which has been obtained by impregnating SiO2 pellets with basic copper carbonate, in the liquid or gas phase.
U.S. Pat. No. 4,739,051A (BASF AG) teaches the preparation of morpholine and piperidine by reaction of DEG or pentanediol with ammonia under hydrogenation conditions in the gas phase at standard pressure and 200° C. over an unsupported Cu/Ni/Al catalyst with yields of 97 and 95%, respectively.
EP 514 692 A2 (BASF AG) discloses processes for preparing amines from alcohols in the presence of catalysts comprising copper and nickel and zirconium oxide and/or aluminum oxide.
DE 198 59 776 A1 (BASF AG) relates to the preparation of amines by reacting alcohols, or aldehydes or ketones, with amines over a catalyst composed of copper and TiO2, to which metallic copper has been added before the shaping of the catalyst material.
EP 440 829 A1 (U.S. Pat. No. 4,910,304) (BASF AG) describes the amination of diols over copper catalysts, especially the preparation of N-methylpiperidine and N-methylmorpholine by reaction of pentanediol or diethylene glycol (DEG) with methylamine and 45% aqueous KOH solution over an unsupported Cu/Al catalyst at 245° C. and 250 bar. The reaction is performed in the liquid phase (trickle mode) (page 3 last paragraph). Suitable catalysts are the catalysts disclosed in DE 24 45 303 A (BASF AG), which are obtainable by heat treatment of a basic copper- and aluminum-comprising carbonate of the general composition CumAl6(CO3)0.5mO3(OH)m+12, where m is any value, including non-integers, from 2 to 6, for example the precipitated copper catalyst disclosed in loc. cit., example 1, which is prepared by treating a solution of copper nitrate and aluminum nitrate with sodium bicarbonate and subsequently washing, drying and heat treating the precipitate.
WO 05/110969 A1 (BASF AG) describes a process for continuously preparing an amine by reacting a primary or secondary alcohol, aldehyde and/or ketone with hydrogen and a nitrogen compound selected from the group of ammonia, primary and secondary amines, at a temperature in the range from 60 to 300° C., in the presence of a copper catalyst, wherein the catalytically active material of the catalyst, before the reduction thereof with hydrogen, comprises 20 to 85% by weight of aluminum oxide (Al2O3), zirconium dioxide (ZrO2), titanium dioxide (TiO2) and/or silicon dioxide (SiO2), and the reaction is effected in the gas phase isothermally in a tubular reactor.
WO 2010/031719 A1 (BASF SE) relates to a process for continuously preparing an amine by reacting a primary or secondary alcohol, aldehyde and/or ketone with hydrogen and a nitrogen compound selected from the group of ammonia, primary and secondary amines, at a temperature in the range from 60 to 300° C., in the presence of a copper- and aluminum-oxide-containing catalyst, wherein the reaction is effected in the gas phase and the catalytically active material of the catalyst, before the reduction thereof with hydrogen, comprises aluminum oxide and oxygen compounds of copper, and the shaped catalyst body is specified.
U.S. Pat. No. 4,487,967 and U.S. Pat. No. 4,665,195 (both Exxon Res. & Eng. Co.) teach the preparation of sterically hindered amino ether alcohols by reaction of corresponding amines with diethylene glycol or polyalkenyl ether glycols. The selectivity problem in the reaction of TBA with DEG owing to the formation of N-tert-butylmorpholine (TBM) is described (U.S. Pat. No. 4,487,967: column 3). The catalysts used are supported and unsupported metals, including Ni/Al2O3/SiO2, Ni—Al, Raney Ni, Raney Cu catalysts. In the case of the copper catalysts mentioned, the TBADG yield is only 6.4% (U.S. Pat. No. 4,487,967, column 6, table 1). In the case of the Ni/Al2O3/SiO2 catalyst, the isolated TBADG yield is only 54% (U.S. Pat. No. 4,487,967, column 5, example 1).
WO 07/021,462 A2 (Exxon-Mobil Res. & Eng. Comp.) relates to the use of dialkylamine glycols or monoalkylamine glycol ethers in acid gas scrubbing, and the preparation thereof by aminating corresponding glycols. Page 15 mentions the preparation of TBADG from DEG and TBA over a nickel catalyst in only 30% yield, and also discusses the selectivity problem (cf. the scheme on page 15).
WO 05/081778 A2 (Exxon-Mobil Res. & Eng. Comp.) describes, inter alia, the synthesis of TBADG from DEG and TBA over supported metal catalysts, the support having specific pore sizes, pore distributions and surface areas (BET). Preference is given to using nickel catalysts (page 3, paragraph [0009]). In all examples, unsupported nickel catalysts are used. Illustrative results are:
Example 6c, page 28, run 27: DEG conversion=72%, molar TBADG:TBM ratio=13,
Example 9, page 31, 8 h: DEG conversion=62.5%, molar TBADG:TBM ratio=15, and
Example 12, page 37, #170-8: DEG conversion=51.9%, TBADG:TBM mass ratio=15.8, i.e. molar TBADG:TBM ratio=14.
Since no selectivities are reported here, no yield can be calculated. At a TBADG selectivity of 80% (based on DEG), the TBADG yield in the best example (example 6c, page 28, run 27) would be approx. 57%.
U.S. Pat. No. 4,405,585 (Exxon Res. & Eng. Comp.) describes the use of strongly sterically hindered secondary amino ether alcohols for selective removal of H2S from a gas comprising CO2 and H2S. Example 1, in column 9, describes the preparation of TBADG from TBA and 2-chloroethoxyethanol.
WO 05/082834 (Exxon-Mobil Res. & Eng. Comp.) describes a process for preparing sterically strongly hindered amino ether alcohols and diaminopolyalkenyl ethers by reaction of a primary amine with polyalkylene glycol at elevated temperature and pressure in the presence of a specific catalyst. The catalyst is characterized in that its preparation involved decomposition of organic metal complexes on a support.
It has been recognized in accordance with the invention that the reaction of DG with TBA over nickel catalysts has the considerable disadvantage from a safety point of view that decomposition products of DG form, which cause a critical situation, for example, in the case of disrupted operation of the reactor (especially power failure). In the amination of DG, for example as a result of decarbonylation, there is enhanced formation of undesired components such as methoxyethanol, methoxyethylamine, methanol, methane (see scheme below). Methoxyethanol is toxic, can be removed from TBADG only with difficulty owing to its physical properties, and can thus lead to problems with regard to specification and product quality.

In order to solve this problem, complex specialty reactors are used in some cases; cf., for example WO 2009/092724 A1 (BASF SE), especially page 10, lines 14-21.